In semiconductor packaging, mold compounds are widely used to encapsulate flip-chip dies and wire-bonded dies to protect the dies against damage from the outside environment. However, direct contact of the mold compounds and active die surfaces may adversely impact the electrical performance of the dies, especially for dies that support high frequency applications. Accordingly, it is desirable to package the dies in an air cavity configuration.
However, die-attach materials used to attach the dies to a carrier may form dendrites in air cavity packages. For instance, the die-attach materials for the dies, which are formed by Gallium nitride (GaN) technology and include GaN field-effect transistors (FETs), have high potential to form dendrites. It is because the GaN FETs require significant negative gate biases, such that there is an electric field formed between the negative-biased gates as cathodes and the die-attach materials (typically coupled to the ground) as anodes. In addition, because the die-attach materials are not sealed off in the air cavity packages, the dendrites of the die-attach materials may grow along side walls of the dies from the anodes towards the cathodes, and eventually cause an electrical short.
Accordingly, there remains a need for improved package designs to inhibit dendrites of die-attach materials without degrading the electronic performance of the dies. Further, there is also a need to keep the final product size effective and cost effective.